The present invention relates to time domain reflectometry, and more particularly to a method of detecting splices in an optical fiber using a two stage filter process applied to noisy data samples acquired by an optical time domain reflectometer.
In an optical time domain reflectometer (OTDR) a light pulse is transmitted through an optical fiber and a reflected signal is received from the optical fiber due to Rayleigh backscattering. The received signal is generally averaged over many transmitted pulses to reduce the noise and is in the form of one or more decaying exponentials with small breaks The decays correspond to the loss characteristics of the optical fiber and sometimes to the artifacts due to a detector in the receiver of the OTDR, and the breaks correspond to splices, either fusion or reflective, that may exist in the optical fiber. As the transmitted light pulse travels through the optical fiber it looses power and the signal to noise ratio (SNR) degrades with the distance traveled. The result is that for small splice losses, i.e., small power losses across a splice joint, a splice in the resulting return signal when displayed may not be readily apparent to an operator since it is lost in the noise. What is desired is a method of detecting splices in an optical fiber in the presence of noise so that the location and amplitude of the splice loss may be determined.